Patent GB-1187895-A (GB)
Title: Automatic Positioning Apparatus for Irradiation.
IPC: A61N5/01
Filed: 1968-04-16
Abstract: 1,187,895. Irradiation apparatus with automatic positioning control. ATOMIC ENERGY OF CANADA Ltd. 16 April, 1968 [10 Aug., 1967], No. 17839/68. Heading H5R. An irradiation apparatus comprises a source of radiation mounted in a housing, a support for a patient under treatment, a plurality of motive means arranged when activated respectively to produce independent relative movements between the housing and the support, in different directions or senses, position sensing means arranged to provide an indication of the actual relative positions of the housing and support, input means to provide an indication of the desired relative positions of the housing and support, and control means to which signals from the position sensing means and the input means are applied and which is arranged automatically to energize the separate motive means to produce the desired relative position of the housing and support and thereby ensure irradiation of a predetermined part of the patient with energy from said source. Preferably the control means is arranged to act upon all the motive means at the same time so that any errors in positioning are corrected by the simultaneous operation of the separate motive means. The input means and the output means may be arranged to provide an indication in digital form of the desired and actual relative positions respectively of the housing and the support. The apparatus may include a register which is arranged initially to contain a number indicative of the desired relative positions, and the position sensing means include a pulse producing device driven by changes in the relative positions of the housing and the support, these pulses being supplied to the register in a manner such as to provide an indication when the desired position is reached. The register may be arranged to count up to a predetermined number, and the number indicative of the desired relative position is the complement of the number of pulses produced when moving to that position, the register thus always indicating the predetermined numbers when the desired position is reached. The preferred input means is an electric typewriter providing appropriate electrical input signals. The apparatus may incorporate an output means to which output from the position sensing means are applied, this output means being arranged when activated to provide an indication or record of the relative positions of the housing and the support. In addition to a pulse producing means, the position sensing means may include a register which can be set to a predetermined number when the housing and the support occupy a first-relative position, pulses from the pulse producing device being algebraically added to the register during subsequent movement of the housing and support so that the resultant change in count may be utilized as an indication of the positional change. The apparatus may include a first register arranged to receive in digital form the indication of the desired relative position in respect of one direction of sense, a second or address register arranged to apply that indication to a third register associated with the motive means associated with that direction or sense, the position sensing means being adapted to add its output pulses algebraically to the count in each register whereby the count in each register indicates when the desired position has been reached. If desired the complement counting technique described above may be utilized. The output means may be such as to provide a written record of the signals supplied to it, and the output means may be combined with the input means in a single integer of apparatus e.g. an electric typewriter.